Add gmachine

gmachine/gmachine.go

@@ -0,0 +1,75 @@
+package gmachine
+
+import (
+	"fmt"
+	"log"
+)
+
+// DefaultMemSize is the number of 64-bit words of memory which will be
+// allocated to a new G-machine by default.
+const DefaultMemSize = 1024
+
+const (
+	OpHALT uint64 = iota
+	OpNOOP
+	OpINCA
+	OpDECA
+	OpSETA
+)
+
+type gMachine struct {
+	// Memory 64-bit words of memory
+	Memory []uint64
+	// P (Program counter)
+	P uint64
+	// A (Register A)
+	A uint64
+	// Debugging flag, if turned on will print OpCodes
+	DebugOn bool
+}
+
+func New() *gMachine {
+	return &gMachine{
+		P:       0,
+		Memory:  make([]uint64, DefaultMemSize),
+		DebugOn: false,
+	}
+}
+
+func (m *gMachine) NewProgram(program []uint64) {
+	copy(m.Memory, program)
+	m.Run()
+}
+
+func (m *gMachine) Run() {
+	for {
+		pointer := m.P
+		m.P++
+		switch m.Memory[pointer] {
+		case OpHALT:
+			m.printIfDebug("OpHALT")
+			return
+		case OpNOOP:
+			m.printIfDebug("OpNOOP")
+		case OpINCA:
+			m.printIfDebug("OpINCA")
+			m.A++
+		case OpDECA:
+			m.printIfDebug("OpDECA")
+			m.A--
+		case OpSETA:
+			m.A = m.Memory[m.P]
+			m.P++
+			m.printIfDebug(fmt.Sprintf("OpSETA %d", m.A))
+		default:
+			m.printIfDebug(fmt.Sprintf("COULD NOT DETERMINE OP CODE, code:%d, pointer:%d", m.Memory[pointer], pointer))
+			panic(pointer)
+		}
+	}
+}
+
+func (m *gMachine) printIfDebug(message string) {
+	if m.DebugOn {
+		log.Println(message)
+	}
+}